The invention relates to producing illumination waveguides.
Illumination waveguides are used in decorative and functional lighting applications. Illumination waveguides typically feature a core through which light is transmitted. The core has a cross-section in which the shortest cross-sectional dimension (e.g., the diameter in the case of waveguides having circular cross-sections) is about one millimeter or larger. Light from a source is coupled into an illumination waveguide and transmitted through the waveguide. The light may be transmitted to an end of the waveguide, providing a point light source, or the light may be transmitted to one or more pre-selected segments of the waveguide where the light is re-directed out of the waveguide in a controlled manner.
An annular cladding surrounds the core and serves to maintain the transmission of light through the core to the preselected location(s) along the waveguide. This property is partially achieved by selecting a cladding having a refractive index lower than the refractive index of the core. However, light may still be scattered from the core (and through the cladding) due to imperfections in the core, cladding, and core/cladding interface. For example, an optically rough inner surface of the cladding, adjacent the core, may cause undesired random scattering of light out of the waveguide.